Oral Administration of Melatonin or Succinyl Melatonin Niosome Gel Benefits 5-FU-Induced Small Intestinal Mucositis Treatment in Mice

Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

The Metformin Immunoregulatory Actions in Tumor Suppression and Normal Tissues Protection

The immune system is the key player in a wide range of responses in normal tissues and tumors to anticancer therapy. Inflammatory and fibrotic responses in normal tissues are the main limitations of chemotherapy, radiotherapy, and also some newer anticancer drugs such as immune checkpoint inhibitors (ICIs). Immune system responses within solid tumors including anti-tumor and tumor-promoting responses can suppress or help tumor growth. Thus, modulation of immune cells and their secretions such as cytokines, growth factors and epigenetic modulators, pro-apoptosis molecules, and some other molecules can be suggested to alleviate side effects in normal tissues and drug-resistance mechanisms in the tumor. Metformin as an anti-diabetes drug has shown intriguing properties such as anti-inflammation, anti-fibrosis, and anticancer effects. Some investigations have uncovered that metformin can ameliorate radiation/chemotherapy toxicity in normal cells and tissues through the modulation of several targets in cells and tissues. These effects of metformin may ameliorate severe inflammatory responses and fibrosis after exposure to ionizing radiation or following treatment with highly toxic chemotherapy drugs. Metformin can suppress the activity of immunosuppressive cells in the tumor through the phosphorylation of AMP-activated protein kinase (AMPK). In addition, metformin may stimulate antigen presentation and maturation of anticancer immune cells, which lead to the induction of anticancer immunity in the tumor. This review aims to explain the detailed mechanisms of normal tissue sparing and tumor suppression during cancer therapy using adjuvant metformin with an emphasis on immune system responses.

Akkermansia muciniphila and its outer membrane protein Amuc_1100 prophylactically attenuate 5-fluorouracil-induced intestinal mucositis

5-Fluorouracil (5-FU) is a chemotherapy drug used to treat tumors. Previous studies have shown that Akkermansia muciniphila (A. muciniphila) and its outer membrane protein, Amuc_1100, alleviate dextran sodium sulfate (DSS)-induced colitis in mice. We investigated the effects of both A. muciniphila and Amuc_1100 on 5-FU-induced intestinal mucosal damage in mice. C57BL/6 mice were gavaged with A. muciniphila or Amuc_1100 daily before, during, and after 5-FU injection for a total of 14 days. By evaluating diarrheal toxicity scores, body weight changes, colonic anatomy images, and histopathology of intestinal injury in these mice, we found that A. muciniphila and Amuc_1100 alleviated 5-FU-induced intestinal mucositis. Quantitative polymerase chain reaction assays of intestinal cytokine mRNA levels demonstrated that both A. muciniphila and Amuc_1100 attenuated the upregulation of intestinal Tumor Necrosis Factor-α (TNF-α) and interleukin-6 (IL-6) induced by 5-FU treatment. In addition, they both reduced 5-FU-induced the NLR family pyrin domain containing 3 (NLRP3) inflammatory vesicle activation. Furthermore, by monitoring the mRNA expression of tight junction proteins in the intestine, we found that A. muciniphila and Amuc_1100 were capable of restoring the damaged intestinal barrier. Notably, A. muciniphila and Amuc_1100 also played a role in altering the structure of the intestinal microbial community. The present study revealed the protective role of both A. muciniphila and Amuc_1100 in the intestinal mucositis caused by 5-FU, providing new insights into treatment options.

Modulation of the immune system by melatonin; implications for cancer therapy

Immune system interactions within the tumour have a key role in the resistance or sensitization of cancer cells to anti-cancer agents. On the other hand, activation of the immune system in normal tissues following chemotherapy or radiotherapy is associated with acute and late effects such as inflammation and fibrosis. Some immune responses can reduce the efficiency of anti-cancer therapy and also promote normal tissue toxicity. Modulation of immune responses can boost the efficiency of anti-tumour therapy and alleviate normal tissue toxicity. Melatonin is a natural body agent that has shown promising results for modulating tumour response to therapy and also alleviating normal tissue toxicity. This review tries to focus on the immunomodulatory actions of melatonin in both tumour and normal tissues. We will explain how anti-cancer drugs may cause toxicity for normal tissues and how tumours can adapt themselves to ionizing radiation and anti-cancer drugs. Then, cellular and molecular mechanisms of immunoregulatory effects of melatonin alone or combined with other anti-cancer agents will be discussed.